This invention relates in general to electric door openers. Conventionally, electric door openers are of such a large size that extensive reworking of the door frame is necessary for installation. Because it is necessary to modify the door frame for installation, installation becomes an expensive and time consuming operation. Numerous variations of complex mechanisms for electric door openers exist in the prior art and result in expensive manufacturing costs.
Numerous patents exist in the prior art in the field of electric door openers and electric strikes. U.S. Pat. No. 3,211,850 issued to Toepfer, U.S. Pat. No. 3,819,215 issued to Fuss, and U.S. Pat. No. 4,211,443 issued to Butts et al are typical of prior art electric door openers. These patents all cover similar inventions and only U.S. Pat. No. 4,211,443 will be discussed in particular.
The mechanism of the electric door strike disclosed is illustrated in FIG. 1 of U.S. Pat. No. 4,211,443 and consists primarily of a solenoid 66, a locking cam 44; a locking lever 32, and a pivotable keeper 80. The combination of the locking cam and locking lever is typical and is also disclosed in U.S. Pat. Nos. 3,189,215 and 3,211,850. This combination in part results in a necessarily large unit and is expensive to manufacture. This type of electric door opener has seen wide spread use and until the occurrence of the present invention, a small and economical electric door opener having the equivalent or superior operating characteristics of prior art electric door openers has not been in existence.
The relevance of the prior art indicated in the present specification should not be given a limited interpretation. A cited prior art item may be found to have relevance in a passage other than the one referred to, or to have relevance in sense different than as stated.